Electric incandescent lamp.



PATBNTED MAY 8, 1906.

W. J. PHELPS.

ELECTRIC INOANDESGENT LAMP.

APPLIOATION FILED JUNE 1.1903.

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l, WILLIAM J. PHELPS, OF DETROIT, MICHIGAN.

ELECTRIC INCANDESCENT LAMP- Specification of Letters Patent.

ratented May 8, 1906.

Application filed June 1,1903. Serial No. 159,547-

To all whom it may concern.-

Be it known that I, WILLIAM J. PHELPS, a citizen of the United States,and a resident of the city of Detroit,- county of Wayne, and State-ofMichigan, have invented certain new and useful Improvements in ElectricIncandescent Lamps, of which the following is declared to be a full,clear, and exact description.

The invention relates to electric incandescent lamps having twofilaments mounted within a single vacuum-bulb and designed to emit lightof varying intensitysuch, for example, as described in prior LettersPatent of the United States No. 603,705, issued to me May 10, 1898.

The present improvement relates particularly to lamps of this typedesigned for use in connection with an electrical supply of high voltageand seeks to provide an effective arrangement of the se arate filamentswithin the vacuum bulb wiiich will prevent shortcircuiting" between themand which will allow the employment of long filaments of highefiiciency, but will prevent them from excessive vibration and fromdrooping.

The invention consists in the features of construction and arrangementof parts set forth in the following description, illustrated 0 in theaccompanying drawings, and more particularly pointed out in the appendedclaim. In the drawings, Figure 1 is an elevation of;

the improved form of lamp. Fig. 2 is a vertical section of the same.

The base of the lamp may be of any wellknown or desired ty e and adaptedto be used with any suitab e form of lamp-holder.

To illustrateihe present improvement, the

Edi'son type of lamp-base is shown, which comprises a screw-shell 10,forming one of the 5 end to hold it securely in place.

lamp -terminals for the reception of current and supporting within itsouter end the glass vacuumbulb 11, the latter being held in place by asuitable composition filling 12. A

' disk 13, of porcelain or other similar material,

mounted within the inner end of screw-shell 10, carries a centralcontact in the form of a tubular rivet 14, which passes through acentral opening in the disk and is flanged at either A bent spring-metalpiece 15 is clamped to the face of the disk 13 by the upper flanged endof the tubular rivet 14, but is insulated from the latter by a suitablewasher 16. The metal piece 15 forms the second terminal of the lamp andengages the central terminal of the lampholder for the reception ofcurrent therefrom. As shown, the upper end of the lamp-terminal 15extends above and normally out of engagement with the contact 14, butmay be depressed into engagement with such contact by any suitablemeans, as, for example, when the lamp is screwed into and out of itsholder or by means within the lamp-holder itself.

Preferably two filaments 17 and 18 of different candle-power areemployed within the vacuum-bulb 11. The filaments are carried on thestem or mount 19 in the neck of the vacuum-bulb 11. The high-powerfilament 17 is connected by leading-in wire 20 with p the lamp-terminal10. The low-power filament 18 is connected by the leading-in wire 21with the lamp-terminal 15. The joined ends of the filaments areconnected, zsshown, to the contact 14, and this connection is preferablyformed of two leading-in wires 22 and 23, twisted togethervandconnected, respectively, to the filaments 17 and 18.

The lamp is designed for use with an electric lighting-current ofconstant or fairly constant potential, and preferably the long orhigh-power filament 17 is of lower resistance er unit of length than theshort low-power lament 18. If the current flows from lampterminal 15 tolamp-terminal 10 through both filaments in series, low-power filamentalone will glow with small candle-power, while the high-power filament17 acts as a relatively dark and dead resistance, cutting down theamount of current used but when spring-terminal 15 is depressed intoengagement with the contact 14 the low-power filament 18 isshort-circuited, and the current will flow through the high-powerfilament 17 alone, which will glow with full candle-power. The partsthus far described may be widely varied without departure from theessentials of the present invention. The lamp base and terminals may beadapted to any suitable lamp-holder and the modification of the flow ofcurrent to the separate filaments may be efiectedin any suitable manner.The electrical connections and arrangements of the filaments may also bevaried. F ilaments of the same candle-power per unit of length-forexample, two of medium candleowermay be used. Also by connectingeading-in wire 20 to the contact 14 and wires 22 and 23 to thelamp-terminal 10 two filaments may be burned, one singly or both inparallel. ever, is as previously described.

In the ordinary single-filament lamp an efficient length of thinfilament is usually provided by employing a filament with a single coiland connecting the coil by an anchor with the stem or mount of the lampto prevent drooping; but with the two filaments in the same bulb ananchor connected to the long filament 17 would interfere with theishortfilament 18 and would be likely to effect a short circuit. To obtain thedesired length of filament in the present construc tion, each of themcomprises a central coiled portion and leg portions,-thelength of suchleg portions being such that the central coiled portion of the low-powerfilament 18 is supported above the central coiled portion of thehigh-power filament 17 within the elongated or pear-shaped bulb 11. Thehelical coil of the high-power filament 17 preferably comprises, asshown, two complete turns, while that of the low-power filament 18 maycomprise three, four, or more complete turns. This arrangementeffectively provides for long filaments of high efficiency, and thehelically-coiledcentral portions tend to pre vent drooping; The presentlamp is designed for use in connection with a high-voltage currentforexample, as high as two hundred andtwenty voltsand to be efificient thefilaments must be of considerable length. To prevent too reat vibrationand drooping of these long filaments, a tip-anchor 24 is connected tothe central coiled portion of the highpower filament 17. This tip'anchormay be of nickel wire or partly of glass and partly of nickel wire, asshown. Astem-anchor 25, preferably of nickel wire, is connected to thecentral coiled portion of the low-power filament 18.

In the manufacture of the lamps the hollow stem or support 20, to whichthe filaments are attached, is provided in the sealing process with aflattened end, as shown, so that the extreme ends of the filaments orthe The preferred arrangement, how

short platinum mounts thereof sealed in the end of the stem necessarilylie in'the same plane; but with a double filament the ex treme ends ofthe filaments are necessarily brought into close relation near theflattened end of the stem. To give the maximum distance between the legsof the filaments and to insure that the legs shall diverge to preventshort-circuiting between them, the central portions or coils of thefilaments 17 and 18 are arranged at an angle to each other and indifferent planes, preferably at right angles,"

as indicated inthe drawings. This arran ement insures that the adjacentlegs oft e separate filaments shall diverge from each other outwardlyfromthe' end of the lampstem, and there is no danger that they will comein contact. 7

Variations from the construction set forth may be readily made withoutdeparture from the essentials of the invention.

Having described my invention, what I claim as new, and desire to secureby Letters Patent, is

An electric incandescent lamp comprising a single vacuum-bulb, twoincandescing filaments therein, a stem extending within said bulb andhaving a flattened end portion to which the ends of the filaments areattached in substantially the same plane, said filaments having centralcoiledportions supported one above the other and arran ed at an angle toeach other and in different p anes, a tip-anchor connected to thecentral coiled portion of the lower filament and a stemanchor connectedto the central coiled portion of the upper filament, the arrangementbeing such that the adjacent legs of the filaments diverge and thecentral coiled portions thereof are held out of contact whereby longfilaments of high efficiency may be employed in a single vacuum-bulb. I

WILLIAM J. PHELPS.

Witnesses:

W. E. PHELPS, CoRA PEARL BLIss'.

